MojoKid writes: Microsoft has several valid reasons why you should upgrade to Windows 8.1, which is free if you already own Windows 8. However, there's a known issue that might give some gamers pause before clicking through in the Windows Store. There have been complaints of mouse problems after applying the Windows 8.1 update, most of which have been related to lag in video games, though Microsoft confirmed there are other potential quirks. Acknowledging the problem, Microsoft says it's also actively investigating the issues and working on a patch.